Soca’s deputy director Steve Coates said the disruption of organised Turkish gangs on their home territory helped cause a heroin “drought” on the streets of Britain which is driving up the wholesale price of the drug.

Turkish gangs traffic around 70% of the 18-23 tonnes of heroin smuggled into the UK each year, Mr Coates told the House of Commons Home Affairs Committee.

But he played down suggestions that Turkish accession to the European Union would increase the supply of the drug by making it easier for gang members to move in and out of the UK.

Turkish EU membership would allow “more streamlined, structured and faster” intelligence sharing between police forces and would deliver advantages in tackling the drug trade at its source, he said.

Soca currently has eight officers based in Istanbul and Ankara, co-operating with Turkish National Police and other law enforcement agencies in tackling the five major crime gangs which dominate the heroin trade.

While Turkish gangs were also involved in organised immigration crime, fraud, money laundering and copyright offences, these are dwarfed by the scale of the heroin trade.

The same “Mr Bigs” have controlled the trade from Turkey for the last 20-25 years, and targeting them in their home country is more effective than arresting gang members in the UK, who are easily replaced, said Mr Coates.

“I think that we can say with a degree of certainty that the shortage of heroin is not exclusively down to law enforcement action, but we have had a significant impact on it,” Mr Coates told the committee.

Thanks to co-operation with Turkish police, “we have been able to reach out and impact these crime groups in a way we have not be able to before”, he said.